Respond thoughtfully and with a respectful tone. Objectify the situation, not the individual you disagreed with. Avoid examples that did not end amicably. There is nothing wrong with disagreeing with your superiors when you are both pursuing the same goal and working as a team. Use examples where you disagreed on an approach to solving a problem and a meeting of the minds was reached.

"I saw an opportunity to outsource an agency that performed well in our industry, better than the agency we were using. After I backed up my suggestion with hard data, my boss decided not to pursue it. He had greater confidence with the agency we were using, saying that they'd explored the option before and it would cost time and resources to get that agency up to speed with the unique vision of our brand. Although I disagreed with their decision, I respected their reasons."

Avoid bad-mouthing your boss or asserting your opinion over theirs. Respecting the chain of command and respectfully working to understand their vision is the goal.